The present invention relates to implantable medical devices, and more particularly to a programmer used to program such medical devices. In accordance with one embodiment, the invention relates to a programmer adapted for use with an implantable spinal cord stimulator (SCS), or similar implantable neural stimulator, and relates to the manner in which the paresthesia resulting from applied electrical stimuli is adjusted or programmed so as to match an area of perceived pain or other need.
Many types of implantable nerve stimulators exist which perform the function of providing selected electrical stimulation through selected groupings of implanted electrodes. An example of such a nerve stimulator is a spinal cord stimulator. One type of spinal cord stimulation system is disclosed in applicants"" copending patent application, xe2x80x9cRechargeable Spinal Cord Stimulator Systemxe2x80x9d, Ser. No. 09/626,010, filed Jul. 26, 2000, which application is incorporated herein by reference. One way of controlling the operating parameters used to control such a spinal cord stimulator is disclosed in applicants"" copending application, xe2x80x9cParameter Context Switching For An Implanted Device,xe2x80x9d Ser. No. 09/668,925, filed Sep. 25, 2000, which application is also incorporated herein by reference. A preferred way of sensing and setting the stimulation parameters associated with such a spinal cord stimulator is taught in applicant Mann""s copending application, xe2x80x9cMagnitude Programming for Implantable Electrical Stimulatorxe2x80x9d, Ser. No. 60/172,167, now U.S. Pat. No. 6,381,496 B1, which patent is likewise incorporated herein by reference.
Spinal cord stimulation systems offer a large number of variables to be programmed. For example, in addition to the variables of stimulation frequency and stimulation current amplitude, the number of electrode contacts that provide the stimulation must be programmed. Moreover, because such selected electrode contacts are typically selected from a relatively large number of contacts, with the number of possible electrode combinations being a large number, there is a need to determine which electrode combination from such large number of possible combinations, provides the optimum stimulation performance for the patient. That is, after initial implantation, it is typically necessary to program many electrode combinations and to test the patient response to each combination. This can be a very time consuming task, both to perform the selected programming of all the electrode combinations, and then to conduct the testing for each selected combination. Optimal device settings, i.e., an optimal electrode combination, is highly dependent upon the location and distribution of stimulating current provided through the selected electrode combination relative to various nerve paths of the body, which in turn varies significantly from patient to patient. Thus, one selected electrode combination that proves effective for one patient, may not prove effective for another patient. Hence, many different electrode combinations must be programmed and tested in a relatively short period of time in order to discover which electrode combination is most effective for a given patient.
Heretofore, the process of optimizing the stimulator device settings has typically involved having the programming clinician simply select an electrode combination and stimulation settings, wait for a patient response, and then intuitively or arbitrarily make changes to the programming in response to patient feedback, wherein the goal is to affect the pain site by paresthesia. (Herein, xe2x80x9cparesthesiaxe2x80x9d is a term used to describe the tingling sensation felt by a patient as a result of application of an electrical stimulus.) Much research has been published showing spinal cord mapping in relation to anatomical areas and neurophysiologic responses to help understand how best electrode arrays should be set up, or programmed, for effective stimulation. Spinal cord mapping has also been associated to dermatome segments of the body.
In U.S. Pat. No. 5,370,672, one way is taught by which an implanted device may be programmed. In accordance with the teachings of the ""672 patent, a patient is provided with a touch sensitive screen on which a representation of the human body is presented. The touch sensitive screen is connected to a suitable computer, and the computer is linked with the implanted device, i.e., stimulus commands may be sent from the computer to the implanted device. The patient then draws a circle around the area of pain he or she is experiencing on the touch sensitive screen using a stylet or other suitable tool. Acting on that information, the computer sends commands to the stimulator to activate an electrode combination in the vicinity of the identified pain area. The patient then draws another circle on the touch sensitive screen indicating where he or she feels the paresthesia resulting from the applied stimulus. The computer then calculates, using predetermined rules, a new electrode combination in an attempt to bring the paresthesia drawing closer to the pain drawing, and then sends a new command to the stimulator to cause it to apply an electrical stimulus to the new electrode combination. The patient responds by drawing another circle on the touch sensitive screen indicating where he or she feels the paresthesia resulting from the stimulus applied to the newly selected electrode combination. This process continues, using the paresthesia location information provided by the patient after stimulating each new electrode combination, in an attempt to bring or move the paresthesia-patient-identified area on the touch sensitive screen over the pain area, initially identified on the touch sensitive screen by the patient. Disadvantageously, this approach requires additional hardware in addition to the programming computer, including a touch sensitive screen and a stylet.
What is needed is a more streamlined approach for programming an implanted device that does not require the use of additional hardware other than the programming computer.
The present invention addresses the above and other needs by allowing a patient to program an implant device, e.g., an implanted spinal cord stimulator (SCS), so that the area of sensed paresthesia resulting from applied electrical stimuli matches the perceived area of pain. Such programming is accomplished through the use of a programming computer, e.g., a laptop or personal handheld computer, linked with the implant device. The computer is programmed to utilize information known in the art regarding anatomical relationships between the spine and the body. The body is divided into dermatomes and/or subdivisions of dermatomes, and a representation of the body, including its dermatomes and/or subdivisions of dermatomes are displayed on the screen (or other display device) associated with the computer. The patient then moves a cursor over the regions of the body displayed on the computer screen. As the patient thus moves the cursor over regions of the body, dermatones or body subdivisions are exposed, allowing the patient to select the region of pain or paresthesia by a click of a mouse or the press of a button.
For example, in one implementation, the patient may select a region of pain by a right mouse click, and a region of paresthesia by a left mouse click. Advantageously, the patient may select as many dermatomes or body segments/regions/subdivisions as necessary to communicate the area of pain or paresthesia to the computer. The computer then uses this information to quickly zero in on an electrode combination and appropriate stimulus parameters so as to create a match (or as close of a match as is possible) between the pain region and the paresthesia region.
One aspect of the invention is directed to a method of programming an implant device. The implant device typically comprises an implantable pulse generator having an implantable electrode array connected thereto. The implantable pulse generator has electrical circuitry therein that generates electrical stimulation pulses in accordance with programming data. The electrical stimulation pulses are delivered to body tissue of a patient through a selected combination of a multiplicity of electrodes on the electrode array. The programming method taught by the invention generally includes the following steps:
(a) creating a data base that maps various electrode combinations to paresthesia regions of the body based on known and collected data;
(b) storing the data base in a programming computer;
(c) displaying a human figure on a display screen of the programming computer, and dividing the human figure into a multiplicity of regions;
(d) selecting one region on the displayed human figure where the patient feels pain;
(e) selecting a combination of electrodes and stimulation parameters adapted to produce paresthesia in the region of pain;
(f) generating stimulation pulses and delivering the stimulation pulses to the selected combination of electrodes through the implantable pulse generator;
(g) identifying a region of paresthesia on the displayed human figure where the stimulation pulses generated in step (f) produce paresthesia;
(h) determining the degree of mismatch between the region of paresthesia identified in step (f) and the region of pain selected in step (d);
(i) if the degree of mismatch exceeds a prescribed level, selecting a new combination of electrodes and stimulation parameters based on the identified region of paresthesia and the degree of mismatch, and repeating steps (f), (g) and (h); and
(j) if the degree of mismatch is less than the prescribed level, programming the implantable pulse generator with the programming data that produces the least mismatch.
Another aspect of the invention is directed to a system for programming an implantable pulse generator. The implantable pulse generator has an implantable electrode array connected thereto. Further, the implantable pulse generator has electrical circuitry therein that generates electrical stimulation pulses in accordance with programming data. These electrical stimulation pulses may be delivered to body tissue of a patient through a selected combination of a multiplicity of electrodes on the electrode array. The system for programming includes the following components:
(a) a programming computer linked to the implantable pulse generator. The programming computer has a display screen, and includes means for generating and displaying a cursor on the screen that may be manually moved around on the screen by a user.
(b) means in the computer for displaying a human figure on the display screen, where the human figure is divided into a multiplicity of regions.
(c) means coupled to the computer for selecting a region on the displayed human figure where the patient feels pain. If necessary, more than one region may be selected (e.g., if the patient feels pain in more than one region).
(d) means in the computer for automatically selecting a combination of electrodes and stimulation parameters adapted to produce paresthesia in the selected region(s) of pain. This selection will initially be made based on information previously programmed into the computer, e.g., a data base, that defines known anatomical relationships between the spine and the body.
(e) means for generating stimulation pulses and delivering the stimulation pulses to the selected combination of electrodes through the implantable pulse generator.
(f) means for identifying a region(s) of paresthesia on the displayed human figure where the stimulation pulses generated in step (e) produce paresthesia.
(g) means in the computer for determining the degree of mismatch between the identified region(s) of paresthesia and the selected region(s) of pain.
(h) means in the computer for selecting a new combination of electrodes and stimulation parameters based on the identified region(s) of paresthesia and the degree of mismatch if the degree of mismatch exceeds a prescribed level. Then, generating stimulation pulses using the new combination of electrodes and stimulation parameters and determining a new degree of mismatch between the pain and paresthesia regions. This process is then repeated as necessary, thereby minimizing in an iterative fashion the degree of mismatch.
(i) means for programming the implantable pulse generator with the programming data that produces the least mismatch.
Yet another aspect of the invention is directed to a programming apparatus for programming an implantable pulse generator. The implantable pulse generator comprises electrical circuitry that generates electrical stimulation pulses controlled by programming data stored in the computer. An electrode array having a multiplicity of electrodes is coupled to the electrical circuitry. Such programming apparatus includes the following elements:
(1) a programming computer linked to the implantable pulse generator, where the programming computer has a display screen, and means for generating and displaying a cursor or equivalent marker on the display screen that may be manually moved around on the display screen by a user;
(2) first program data stored in the programming computer that causes a human figure to be displayed on the display screen, where the human figure is divided into a multiplicity of regions;
(3) means coupled to the cursor for selecting at least one region on the displayed human figure as a location where the patient feels pain;
(4) second program data stored in the programming computer that causes a combination of electrodes and stimulation parameters to be selected that are adapted to produce paresthesia in the same general location where the patient feels pain;
(5) third program data stored in the programming computer that determines the degree of mismatch between the location where the patient feels pain and the location where the patient feels paresthesia as a result of stimulation pulses produced by the second program data;
(6) fourth program data stored in the programming computer that causes a new combination of electrodes and stimulating parameters to be selected that are adapted to minimize the degree of mismatch between the location where the patient feels pain and the location where the patient feels paresthesia as a result of recently applied stimulation pulses; and
(7) fifth program data stored in the programming computer that causes the combination of electrodes and stimulation parameters that minimize the degree of mismatch to be included in the programming data that thereafter controls the operation of the implantable pulse generator.
It is thus a feature of the present invention to provide a programming device for use with an implantable stimulator, such as an implantable spinal cord stimulator, that allows the patient to easily identify a region of pain and then a region of paresthesia, so that the programming device may then automatically change the selected stimulation parameters, including the selected combinations of electrodes, to cause the region of paresthesia to overlap or merge with the region of pain, thereby alleviating the pain.